Unloading device



June 8, 1954 w. R. GROVES 2,680,447 UNLOADING DEVICE Filed March 6, 1950 2 Sheets-Sheet l June 8, 1954 w, GROVES 2,680,447

UNLOADING DEVICE Filed March 6, 1950' 2 Sheets-Sheet 2 Patented June 8, 1954 UNITED STATES PATENT OFFICE 2,680,447 UNLOADIN G DEVICE Walter Robert Groves, London, England, assignor to British Industrial Plastics Limited, London, England, a British company Application March 6, 1950, Serial No. 147,795

Claims priority, application Great Britain March 7, 1949 6 Claims. (01. 137-108) This invention relates to cut-out valves which piston via a restriction to the other side of the control a fluid pressure supply to a fluid pressure larger piston and to an exhaust pipe.

fluid pressure supply in said fluid pressure syspreferably coaxial. here are certain advantem is hereinafter termed supply pressure, and tages to be obtained by making the area of the the fluid pressure in said fluid pressure system face of the smaller piston which is acted upon is hereinafter termed system pressure. Such by the supply pressure slightly greater than the a cut-out valve is herein defined as a valve which, 10 area of the face of the main valve which is also sure system to escape at full pressure as in a desi n, point of view,

relief valve, opens wide so as to reduce the supply There may suitably be provided, means for pressure to some value at or near zero. adjusting said restriction from the outside of the The invention essentially relates to such cutcasing.

' The restriction has the purpose of causing a operably associated withasmaller-piston adapted differential pressure on the two sides of the t be a t p n y a system pressure so as to larger piston and may suitably comprise an ad- A cut-Out valve o t is yp is described in 00 As an illustration of the invention, a suitable my prior British Patent but the device will now be described by reference to the struction of this valve involves certain disadaccbmpanying drawing in whi h;

v t h main d dv is that the Figure 1 is a sectional elevation of the device duct leading from the main valve and through using valv restri tion, and wh ch the upp y p u is relieved is eonsti- Figure 2 is a sectional elevation of part of that the fluid pressu e pp is adapted to s is coaxial with stems in and II of the main valve between th m Valve and that face of the l and within which operates a small piston it. small r pi ton not t d p n by h system preswhich is integral with the stem 10. The di- On the underside of the valve head 6 is another cylinder 14 coaxial with the cylinder 9 and within which operates a large piston l5, adapted to contact the stem ll of the valve head 1. The face area or the large piston i5 is 8-10 times greater than the area circumscribed by the .valveseating 8. n the underside of the piston I is a poweriul spring 16 which acts between the of the cylinder M and a spring plate 51 bearing on the center of the underside of the piston. through a small polished ball bearing l8to allowa constant axial thrust of the spring. l6..on .the piston it, the thrust constituting loading of the main valve 1. The loading on the spring I6 is adjustable by means of a screw 19.

A passage 29 connects the top .half or the cylinder M to a lightly spring-loaded valve H, e; g,

arranged to lift at about 8 p. s. i., contained in the outer casing l and adjustable by a leak aperture valve 2 i. A passage 24 connects theivalve'2l ;to a storage tank or to a pump means providing the supply pressure. Another passage 25 connects the passage to the cylinder on the underside of the piston.

In Figure 2 there is shown the valve 2\ replaced by a cock 25 which is adjustable by a screw 21.

In the working of this device under normal conditions thenon-return valve 5 is open and the pump is charging the valve chamber l. The supply pressure has no influence on the main valve 1 at this stage since its pressure thereon is counteracted by its pressure against the underside of the piston 12. The only forces then to be considered are. the spring Hi acting upwards on the underside of the piston l5 and the system pressure acting downs wards on the upper side of the piston. l2. So long as the predetermined loading on spring. :8 exerts more force than the system pressure, the main valve '1' will remain closed, but as soon as the system pressure exceeds a predetermined cutout value the spring 19 will be overcome by the system pressure acting upon the upper'side of the piston l2 and reduce the pressure in the valve chamber 4, the non-return valve then automatically closing to maintain the pressure in the pressure system. The fluid flowing past the cracked main valve! will build up a small pressure differential between the two sides of the piston 15 due to the restriction constituted by the valve 2| or the cock and this will cause the piston IE: to movedownwardly to compress the spring l6 and relieve the spring loading on the valve 1. The main valve will then open wide as a result of the increased pressure diiierential between the system pressure which acts on the top of the small piston l2 and the pressure in the valve chamber 4, thereby relieving the supply pressure practically to zero.

As soon as the system pressure "falls below the predetermined cut-in value the .springl6 will overcome the combination of the said pressure difierential and the pressure exerted by thesystern pressure and the main valve will begin to close thereby reducing the flow of fluid past it. This drop in flow will reduce the said pressure differential and spring it will thenibe enabled to force the main valve 1 onto its seating 8.

A typical working range is for the cut-in value to be 950 p. s. i. and the cut-out value 1050 p. s. i.

I claim:

In a cut-out valve device, the combination bottom end.

the springscrew 22. A- 23 is disposed in the head of the the pressure system through the main valve 1 will crack and munication let and biased to closed position away from said of a housing having an inlet for fluid under pressure and an outlet for fluid under pressure, a main duct passing through said housing and connecting said inlet to said outlet, a relatively small cylinder projecting laterally in one direction from saidf-main-duct and communicating at one end therewith, a relatively small piston in said cylinder having one end subject to pressure in said main duct, a relatively large cylinder projecting laterally in the opposite direction from said duct, said housingbeingprovided with a port between said relatively large cylinder and said main duct, a main valve engageable with the end of said port remote from said main duct and movable away from thelatter toopen position, said valve being connected to said relatively small piston, a relatively large piston in said relatively large cylinder engaging said valve, spring means in said relatively large cylinder urging said relatively large piston toward said main duct to bias said valve toclosed position, a differential fluid pressure passage-connected to" the end or said relatively large cylinder adiacentsaid port and having a restriction therein,.a check valve controlling combetween-said main duct and said outoutlet, and an unrestricted passage. communicating between said outlet and said relatively small cylinder at the end of the latter remote from said main duct to subject the other end of said relatively small piston to pressures in said outlet.

2. A'cut-out valve device according to claim 1 comprising a spring loadedvalve serving to adjust saidrestriction.

3. A cut-out valve device according to claimzl comprising means for adjusting said restriction, said means comprising a: valve, and means for imposing a predeterminedlimit upon movement of said valve.

4; A cut-out valve .deviceaccording toclaim 1 provided with manually operable adjusting means foriadjusting the restriction in said differential fluid. pressure passage.

5; A cut-out valve device according to claim 1 in which said spring'means comprises a com: pression spring in the end of said relatively large cylinder remote from said main duct, 2. plate between said compression springand said relatively large piston and forming a scatter said spring, and'a'ball interposed between said plate and said relatively large pistonaxially thereof.

6. A'cut-out valve device according to claiml in. which said main valve is formed with a stem abutting'said relatively large piston.

References Cited in the file of this patent UNITED STATES PATENTS 

